1. Field of the Invention
The apparatus of the present invention relates generally to bar code readers and more specifically to a static optical bar code reader which can identify a stationary bar code.
2. Description of the Prior Art
Optical bar code readers are well known in the art and typically require relative movement between an optical reading device and the bar code. In point of sale systems commonly found in grocery stores, a coded item for sale is moved relative to an optical reading device disposed in the check-out counter. In other systems typically found in clothing stores, a hand-held wand or a similar device is moved relative to a bar code located on the price tag.
In an inventory or warehousing system in which a coded article is disposed in a stationary position for a prolonged period of time, the need for relative movement between the bar code reader and the bar code is a particulary disadvantageous requirement. Relative movement between the bar code and bar code reader would require the physical movement of the item or alternatively would require the insertion of a bar code reading device into the storage area. Both of these requirements are undersirable in many instances.
A particulary undesirable instance occurs in the manufacture of semiconductor devices. Semiconductor wafers are typically processed in batches of twenty-five or fifty. These wafers are held in cassettes in groups of twenty-five between processing steps. In order to maintain cleanliness, these cassettes are placed in a cassette box. These cassette boxes are typically made of plastic, and may have latches to close the lid. The cassette boxes may also hold one or two cassettes.
A major problem in the manufacturing of integrated circuits or semiconductor wafers is the lack of knowledge concerning position of inventory in the manufacturing process. Typically, a piece of paper is taped to a cassette box with the identity and progress through the process indicated on the paper. However, the actual physical position of the cassette box is unknown. The box may be on a table, or in a rack, or stacked on the floor. If it is needed, a person is required to go and look for the box. It is possible that several hundred boxes are in process at the same time, thus positive control and location identification are missing. The addition of a bar code to the boxes would greatly facilitate the positive identification of these boxes. Movement of the boxes, however, would tend to generate dust particles and would interfere with the manufacturing process.
Accordingly, there is a need for an optical bar code reader which can identify a stationary article such as a cassette box and provide an indication of its location without any relative movement between the box and the bar code reader.